Electrical recorder



IDLE CIRCUITS REGISTER II I BUS Y CIRCUITS PEG/S TE R c. E. GERMANTON ELECTRICAL RECORDER Filed Dec. so. 1936 May .3, 1938.

N V. m RN 0 mm. m N A Z W 5 6 V, 8

Patented May 3, 1938 UNITED STATES PATENT oFFIcE ELECTRICAL RECORDER Application December 30, 1936, Serial No. 118,249

Claims.

This invention relates to electrical counting systems and more particularly to holding time recorders adapted for use in a telephone system.

In the operation and maintenance of telephone 5 exchange systems it is necessary to obtain the holding time of a group of circuits as an adjunct in making traific studies in order that a determination may be made as to the adequacy of the circuits to handle the traific load. Heretofore it has been the practice to obtain the holding time of each circuit individually and from the individual records to compute the holdingtime of a group of circuits and thereby determine the adequacy of the group of circuits to handle the traffic load. It is the object of the present invention to provide facilities for obtaining the average holding time for a group of circuits with less apparatus and no more clerical effort than has heretofore been required.

In accordance with the present invention the holding time recorder for a group of forty-four circuits comprises a rotary step-by-step selector switch, a start key, two peg count registers and two oppositely poled copper oxide rectifiers. The

selector switch when started by the operation of the start key successively tests the circuits of the group being observed and during each cycle thereof one of the registers will be operated once for each idle circuit tested and the other register will be operated once for each busy circuit tested.

On successive cycles the two sets of idle and busy registrations will be added on the two registers.

The sum of the registrations thus made, divided by 44, or the number of circuits tested during each cycle, will thus give the number of cycles made during the period of the observation or test. vSince the selector switch will continue in operation so long as the start key is operated and will complete the last cycle after the key is released, by dividing the registration on the busy circuit register by the number of completed cycles, the average number of circuits which were busy during the observation period will be obtained. This figure multiplied by the elapsed time of the observation period and divided by the total number of calls made during the period, as indicated by the usual peg count register, will give the average holding time per call.

For a more complete understanding of the in-, vention reference may be had to the following detailed description taken in connection with the drawing.

Each circuit to be tested for its busy or idle condition is represented by a relay 6 of which only six of the group of forty-four which may be tested by the single holding time recorder have been shown. Whenany one of the circuits is busy its corresponding relay 6 will be energized and will apply ground over its contacts to a terminal in either bank I or bank 8 of the rotary step-by-tep selector switch 50.

The selector switch 50 is provided with a stepping magnet I5 and four wipers ll, l2, l3 and M, the wipers l l and i2 being both connected to conductor I 6 and positioned degrees apart on the switch shaft and the wipers l3 and I4 being both connected through resistance H to 48-volt battery It and similarly positioned 180 degrees apart on the switch shaft. As previously stated, the terminals of banks 1 and 8 with which wipers H and i2 are associated, are connected to contacts of the relays 8 and with the exception of the first terminal in bank 9, all of the terminals of banks 9 and iii are strapped together and connected to conductor I6.

Two peg count registers I9 and 20 are provided, the register 19, which functions to count the number of circuits found to be busy, being connected in a circuit from 24-volt battery 2! through the copper oxide rectifier 22 and the back contact of stepping magnet E5 to conductor l6 and the register 20, which functions to count the number of circuits found to be idle, being connected in a circuit from 24-volt battery 2! through copper oxide rectifier 23 and the back contact of stepping magnet IE to conductor it. Either register upon operating establishes over its armature contacts an operating circuit for the stepping magnet l5.

Normally, the switch 56 is atrest with its wipers standing in the positions illustrated. To start a test a reading is first taken from each of the registers i Q and 2E! and the key 26 is operated. It will be assumed that the first circuit of the group to be observed is busy as indicated by the operated condition of relay 6'. Upon the operation of key 24 a circuit is established over which current tends to flow from thepositive or grounded terminals of the central ofiice batteries 48 and El over the contacts of the operated relay 6', contacts of key 24, the first terminal of bank 7 and wiper H engaged therewith, conductor I6, back contact of magnet [5 to a point between the rectifiers 22 and v 23, and thence in parallel through rectifier 22 and winding of register [9 and through rectifier Z3 and winding of register 28 to the negative terminal of Zl-volt battery '21. Rectifier 22 is so poled as to oifer a low resistance to the flow of current over the branch of the circuit traced therethrough and consequently the busy register I9 is operated, but since rectifier 23 is poled oppositely and therefore offers a high resistance to the flow of current over the branch of the circuit traced therethrough, the idle register 20 is not operated at this time.

The operation of key 24 also establishes a second circuit over which current tends to flow from the positive or grounded terminal of 24-volt battery 2|, through battery 2 thence in parallel through the winding of register l9 and rectifier 22 and through the winding of register 29 and rectifier 23, thence over the back contact of magnet I5, conductor l6, wiper H and the first terminal of bank I with which it is in engagement, contacts of key 24, the first terminal of bank 9 and wiper l3 engaged therewith, through resistance I7 and the 48-volt battery Hi to ground, but since the relay 6 of the circuit under observation has been assumed to be operated, battery H! is shunted by the connection of ground over wiper l3 and therefore no eifective current flows over the second circuit.

Register i9 upon operating makes a registration of the fact that the first circuit tested is busy and closes its contacts thereby establishing an operating circuit for stepping magnet l5 extending from battery 2| over the contacts of register l9 to ground through the winding of magnet l5. Magnet I5 thereupon operates preparatory to advancing the wipers of switch 59 and opens its back contact thereby releasing the operated register I9 which in turn opens the operating circuit of magnet l5. Magnet l5 upon releasing now advances the wipers of switch 59 one step, in which position wiper engages a terminal of its bank connected to the contacts of relay 6 of the second circuit under observation.

It will now be assumed that the second circuit is also busy as indicated by the operated condition of its associated relay 5 The first circuit above traced is now established and current flows from ground over the contacts of relay 9*, the second terminal of bank and wiper II in engagement therewith, and thence through rectifier 22 and the winding of register I9 to the negative terminal of 24-volt battery 2|, again operating register l9. The second circuit above traced is also reestablished, but at this time from battery 2|, as traced to conductor l6, thence over the strapped terminals of banks l and 9, wiper i3 in engagement with the second terminal of bank 9, through resistance I1 and battery l8. This circuit is, however, ineffective since with relay 6 operated, battery l8 is shunted by ground applied over the contacts of relay wiper H, conductor I6, terminal of bank 9 and wiper i3. Register i9 upon operating registers the fact that the second circuit tested is busy and again causes the operation of magnet I5 which opens the operating circuit of register l9 and thereby causes the release of magnet i5 and the advance of the wipers of switch 59 another step. Wiper now engages a terminal of its bank 1 connected to the contacts of the relay (not shown), corresponding to relay 5 of the third circuit under observation.

It will be assumed that all of the succeeding circuits up to and including the twenty-first circuit are busy and that in the manner previously described, the switch 59 is advanced step by step to test these circuits and to register their busy condition on the busy register l9. When the switch has thus been advanced to position wipers H and IS on the twenty-second terminals of their respective banks 1 and 9, a test is made to determine the busy or idle condition of the twenty-second circuit, the relay 6 of which is disclosed. It will now be assumed that this circuit is idle and that therefore relay 6 is not operated. The first circuit above traced extending over wiper conductor l6 and thence in parallel through the windings of registers |9 and 26 to the negative terminal of 24-volt battery 2|, is not now effective since no ground is connected to the twenty-second terminal of bank 1 with which wiper H is now engaged and therefore register l9 does not operate.

The second circuit above traced is efiective, however, since the 48-volt battery It is not now shunted by ground over wiper H and contacts of relay 6 and current therefore fiows from the positive or grounded terminal of battery 2i, through battery 2|, winding of register 20 and rectifier 23 and in parallel through the winding of register l9 and rectifier 22, back contact of magnet l5, conductor l6, bank terminals of banks It and 9, wiper |3 engaged with the twenty-second terminal of bank 9, through resistance I1 and battery M3 to ground. Rectifier 23 is so poled as to offer a low resistance to the passage of current over the branch of the circuit extending through the winding of register 20 and register 29 operates, but rectifier 22 now offers a high resistance to the passage of current over the branch of the circuit extending through the winding of register l9 and register i9 does not operate. Register 20 upon operating, registers the fact that the twenty-second circuit under test is idle and at its contacts establishes the operating circuit of magnet l5. Magnet l5 now operates preparatory to advancing the wipers of switch 50 and at its contacts opens the operating circuit of register 29 which thereupon releases and opens the operating circuit of magnet I5. Magnet l5 upon releasing now advances the wipers of switch 59 one step. Wipers l2 and I4 now engage the first terminals of their respective banks 8 and H] in which position a test is made for the busy or idle condition of the circuit represented by relay 6 In a similar manner, circuits twenty-three to forty-four inclusive are tested in succession, wipers and I3 being advanced into engagement with the first terminals of their banks after the forty-fourth circuit, represented by relay 6 has been tested. The recorder will now have completed one cycle of operation and if the key 24 is still operated, a second cycle of operation will be started during which the forty-four circuits will again be tested. If during any cycle the start key 24 is released, the switch 50 continues to advance to complete the cycle, but will come to rest when its wiper engages the first terminal of its bank. With key 24 released, no testing circuit will be completed through either register l9 or register 29 and consequently the circuit of stepping magnet |5 will not be closed to further advance the wipers of switch 59.

To compute the average holding time for each call initiated over the circuits under observation it will be assumed as an example, that at the beginning of the observation period the reading taken of the busy register l9 and idle register 2|! are 1536 and 1421, respectively, and that at the end of the observation period the readings are 2031 and 1586, respectively. The busy register |9 will have therefore registered 495 busy circuits and the idle register 20 will have registered 165 idle circuits, or the sum of the advance of the two registers will be 660 indicating that 660 circuit tests have been made. Since the recording circuit tests 44 circuits during each cycle thereof, by dividing 660 by 44 it "follows that the recording circuit will have completed 15 cycles. During the testing period the busyregister has'recorded, as assumed, 495 busycircuit conditions and thus by dividing this registration by the number of completed cycles, or 15, it is thereby determined that an average of 33 circuits were found to be busy during the observation period. If it now be assumed that the elapsed time of the observation period was 55 seconds and that during that period the regular peg count register (not shown) has indicated that fifteen calls have been initiated, then the elapsed average holding time for each call may be computed by multiplying the average number of circuits busy during the observation period, or 33, by the elapsed time or 55 seconds, and dividing the product by 15, or the number of calls initiated, thus giving an average holding time of 121 seconds per call.

The formula by which the holding time H can be computed is derived as follows:

Let n=number of circuits to be observed t elapsed time of observation f=number of cycles performed by the recorder B=number of busy circuits observed I number of idle circuits observed A=average number of circuits busy during the observation period C=number of calls initiated during the observation period I-I=average holding time.

(1) Then tA 3 c H (4) and substituting (2) into (3) f tB -e-re and again substituting (1) into (4) iB tBn (B+I)C c(B+1) In the foregoing discussion a group of fortyfour circuits was assumed. If, however, there are less than forty-four circuits in the group, terminals of the banks 7 and 8 not associated with circuits may be left vacant in which case the idle register 28 will be operated each time one of the wipers H or 12 engages a vacant terminal, but the method of obtaining the holding time will be unchanged. If only twenty-two or less circuits are to be observed they may be multiplied to corresponding terminals of banks '5 and 8 in which case the circuits would be tested twice per cycle which is an advantage since the smaller the group the greater is the percentage diiference caused by one call more or less. If more than forty-four circuits are to be observed as a group, either two separate recorder circuits, one for each group of forty-four circuits may be employed, or the capacity of the recorder may be doubled by the addition of banks and wipers and suitable switching equipment.

What is claimed is:

1. In a traific recorder for recording the traflic conditions in a group ofcircuits, a selector switch for successively testing the idle or busy condition of said circuits, a register for counting the number of idle circuits tested, a register'for'counting the number of busy circuits tested, an operating circuit for said registers extending through their windings in parallel and over the test wiper of said switch, means for selectively operating said registers in accordance with the idle or busy condition of the circuits tested, and a stepping circuit for said switch controlled by the operation of either one of said registers.

2. In a trafiic recorder for recording the trafiic conditions in a group of circuits, a selector switch for successively testing the idle or busy condition of said circuits, a register for counting the number of idle circuits tested, a register for counting the number of busy circuits tested, a polarizing device connected in series with the winding of each of said registers, an operating circuit for said registers extending over the test wiper of said switch and thence by parallel paths through the windings of said registers and serially connected polarizing devices whereby said registers are selectively operated in accordance with the idle or busy condition of the circuits tested, and a stepping circuit for said switch controlled by the operation of either one of said registers.

3. In a traffic recorder for recording the traflic conditions in a group of circuits, a selector switch for successively testing the idle or busy condition of said circuits, a register for counting the number of idle circuits tested, a rectifier connected in series with the winding thereof, a register for counting the number of busy circuits tested, an oppositely poled rectifier connected in series with the windingof said second register, an operating circuit for said registers extending over the test wiper of said switch and thence by parallel paths through the windings of said registers and serially connected rectifiers whereby said registers are selectively operated in accordance with the idle or busy condition of the circuits tested, and a stepping circuit for said switch controlled by the operation of either one of said registers.

4. In a trafiic recorder for recording the traflic conditions in a group of circuits, the idle condition of any circuit being signified by an opencircuit condition on its test terminal and the busy condition being signified by ground on its test terminal, a selector switch for successively testing the test terminals of said circuits, a first register for counting the number of idle circuits tested, a rectifier connected in series with the winding thereof, a register for counting the number of busy circuits tested, an oppositely poled rectifier connected in series with the winding of said second register, an operating circuit for said registers including oppositely poled batteries of different potential and extending by parallel paths through the windings of said registers and serially connected rectifiers, a shunt circuit for one of said batteries extending over the test wiper of said switch, the non-completion or completion of which in each position of said selector switch, in accordance with the idle or busy condition of the circuit being tested, causes the operation of said first or said second register, and a stepping circuit for said switch controlled by the operation of either one of said registers.

5. In a traffic recorder for recording the traffic conditions in a group of circuits, a selector switch for successively testing the idle or busy condition of said circuits during each operating cycle thereof, a register for counting the number of .idle circuits tested, a register for counting the number of circuits tested, means for selectively operating said registers in accordance with the idle or busy condition of the; circuits tested, a stepping circuit for said switch controlled by the operation of either one of said registers, and a.

start key operative to initiate the advance of said switch and to cause said switch to advance through one or more complete cycles so long as key is maintained operated.

CHARLES E. GERMANTON. 

